1. Field of the Invention
The present invention relates to a high-performance semiconductor laser device for use in an image display device such as a laser display device, and an image display device incorporated with the semiconductor laser device.
2. Description of the Background Art
In recent years, a large-screened and thin flat panel display device, as represented by plasma display devices or liquid crystal display devices, has been rapidly spread. A laser display device is being developed, as an example of a thin flat panel display device having a larger screen and a larger luminance. A semiconductor laser device with high luminance output and operable at a low-consumption electric power is used as a light source of the laser display device.
Watt-class high-output performance is required for the semiconductor laser device. In view of this, there is used a so-called multi-stripe semiconductor laser element constructed in such a manner that multiple stripe active regions are formed in the identical semiconductor laser element.
In the semiconductor laser device provided with the multi-stripe semiconductor laser element, it is required to uniformly supply a large electric current to multiple stripe electrodes for high-output performance. In view of this, some improvements are proposed by forming a wiring on a base block where the semiconductor laser element is mounted, or forming a wiring on the semiconductor laser element. There is proposed a first conventional art as an example of the improvements. In the first conventional art, electrode wiring patterns are formed independently of each other on a surface of a semiconductor laser element, and the electrode wiring patterns are electrically connected to multi-stripe electrodes, respectively (see e.g. Japanese Unexamined Patent Publication No. Hei 7-321399, Japanese Unexamined Patent Publication No. Hei 7-147453, and Japanese Unexamined Patent Publication No. 2005-45146). In the first conventional art, the electrode wiring patterns connected to the respective stripe electrodes are electrically connected to a conductive wire by an electrode pad provided in the periphery on the surface of the semiconductor laser element for current supply. In this arrangement, the multi-stripe semiconductor laser device is allowed to emit multiple laser beams.
A second conventional art discloses another multi-stripe semiconductor laser device having a wiring arrangement in the case where multiple electrodes are connected to stripe electrodes individually (see e.g. Japanese Unexamined Patent Publication No. 2003-23200). Specifically, the second conventional art discloses an example of wiring pattern configured in such a manner that an electrode pad is provided at a position to avoid contact with a conductive wire, in the case where the electrode pad and the other electrode are connected to each other by the conductive wire.
Since a watt-class high-output performance is required to drive the semiconductor laser device, a large electric current supply is required, which results in a large electric power consumption. As a result of the large electric power consumption, the semiconductor laser device is unduly heated. Unless appropriate cooling is conducted, supply of a larger electric current to the semiconductor laser device is required to maintain the watt-class high-output performance. As the further heating progresses, it may be impossible to secure the watt-class high-output performance of the semiconductor laser device, or the semiconductor laser device may be degraded.
In order to eliminate the above drawbacks, there is proposed a third conventional art. In the third conventional art, a semiconductor laser element or a semiconductor laser array element is mounted in a casing or a housing, and a coolant is allowed to flow in the casing or the housing. The semiconductor laser element or the semiconductor laser array element is prevented from being heated by directly cooling the semiconductor laser element or the semiconductor laser array element by the coolant, followed by drawing the coolant from the casing or a like member(see e.g. Japanese Unexamined Patent Publication No. Hei 8-116138, and Japanese Unexamined Patent Publication No. 2005-72549). The third conventional art is directed to enhance cooling effect by directly contacting the coolant with at least one of the surfaces of the semiconductor laser element or the semiconductor laser array element, and keeping cooling the surface by flow of the coolant.
There is proposed a fourth conventional art of cooling, with a coolant, a solid-state laser device incorporated with a semiconductor laser element as an excitation light source (see e.g. Japanese Unexamined Patent Publication No. Hei 5-211361 and Japanese Unexamined Patent Publication No. Hei 7-202332). Specifically, in the fourth conventional art, a coolant is drawn into a casing or a like member in which the entirety of the solid-state laser device including the semiconductor laser element is accommodated to directly cool the semiconductor laser element as an excitation light source or the solid-state laser device. This arrangement is advantageous in suppressing a temperature rise of the semiconductor laser element or the solid-state laser device, and stably maintaining the high-output performance of the semiconductor laser element or the solid-state laser device.
In the case where the multi-stripe semiconductor laser device is used as a light source of an image display device such as a panel display device, supply of a larger electric current is required, as compared with a case of using the semiconductor laser device in an optical disk device, a printer, or a like device. In driving the multi-stripe semiconductor laser device in the image display device, unless a heat generated in the stripe active regions is rapidly released from the active regions, the laser output may be saturated by the heat, thereby obstructing the high-output performance. Also, since a large electric current is supplied to the stripe active regions, an electric current flowing in a direction parallel to the stripe electrodes may be fluctuated, which may increase an operation current. As a result, another drawback such as unduly increase of an operation electric power may occur. Also, an increased electric current may degrade the semiconductor laser device.
The first and the second conventional arts disclose a wiring method or a conductive wire mounting method to solve the problems relating to mounting a multi-stripe semiconductor laser device. However, there is not disclosed a method for effectively releasing a heat generated in supplying a large electric current to a semiconductor laser device, or a method for uniformly supplying an electric current to stripe active regions.
The third and the fourth conventional arts disclose an approach of directly cooling an emission point of a semiconductor laser element, a laser chip, or a laser bar, but do not disclose an approach of efficiently cooling active regions of a semiconductor laser element. The third and the fourth conventional arts disclose an arrangement of drawing a coolant into a casing or a like member to directly cool a semiconductor laser element, followed by drawing the coolant from the casing or the like member, but do not disclose an arrangement of flowing a coolant to efficiently cool a laser beam emission end of a semiconductor laser element, or active regions for amplifying the laser beams; or an arrangement of efficiently releasing a heat by transferring the heat to a coolant. Further, the third and the fourth conventional arts do not disclose a safety-oriented arrangement of suspending an operation of a semiconductor laser device in the case where the semiconductor laser device is tilted by e.g. tipping over.